I worked out a bunch more Llyffws numbers -- all the way up to 100 (sean/senc-fint). I still don't know how you write any of them. We'll start over from the beginning:
yn = 1
dw = 2
trei = 3
catra = 4
senc = 5
sis = 6
sep = 7
wit = 8
nwff = 9
dis = 10
ons = 11
dus = 12
trais = 13
cators = 14
cens = 15
cens e yn = 16
cens e ddw = 17
cens e drei = 18
cens e gatra = 19
fint = 20
fint e yn, ddw, ... nwff = 21-29
dw-gens = 30
dw-gens e yn ... nwff = 30-39
dw-gens e ddis / dw-fint = 40
dw-fint e yn ... gatra = 41-45
trei-gens / dw-fint e senc = 45
trei-gens e yn ... gatra / dw-fint e sis ... nwff = 46-49
trei-gens e senc / dw-fint e ddis = 50
...
catra-gens / trei-fint = 60
...
trei-fint e gens = 75
...
catra-fint = 80
...
sis-cens / catra-fint e ddis = 90
...
sis-cens e ddis / senc-fint / sean = 100

So, there you have it, a mixed-base system. The Leafoosish aren't very big on base 10, since their ancestors were Welsh-speaking and used a lot of base 20, and before that they used some cat language that used base 15. Or maybe it was really 18. Anyway, you get the idea. You can probably see the initial consonant mutations, but I'm pointing them out so it's less confusing: dis (10) => catra-fint e ddis (90, four-twenty and ten, "quatre-vingts-dix"), just to give you an example. It's the soft mutation, which is all Llyffws has in modern times.

1: ono (on-oo)
2: deo (deh-oo)
3: tre (treh)
4: cuatra (kat-rah)
5: cuinxa (kin-chah)
6: ses (sess)
7: seit (seyt)
8: oxa (och-ah)
9: nove (noh-veh)
10: diex (dee-ech)

In "cagieje" (it has no English name yet)

Numbers in Avdenio:
1 - eo
2 - dus
3 - teles
4 - ion
5 - vantje
6 - sjeste
7 - seun
8 - lav
9 - tomed
10 - sef

Here are the numbers in "misplaced-stress":
in - 1
du - 2
tres - 3
cuatre - 4
cuinc - 5
ses - 6
set - 7
oit - 8
nov - 9
des - 10

And a try at the Erilish numbers:
oin - 1
dau - 2
tri - 3
ketwar - 4
pink - 5
sweks - 6
sets - 7
ots - 8
nau - 9
dek - 10

11, 12, and so on would probably be something to the effect of oin ar dhek, dau ar dhek ("one on ten", "two on ten"), etc. Not yet sure how lenition is marked, so the spelling of that may be different from what I've given.

numbers are still in development. But I will say that Meikar uses a Base-5 system!

Ma(ka) - 1
E(mi) - 2
Me(i) - 3
Sho - 4
Pu(n) - 5 (Or by base-5 standards, 10)

Then, semi-complex numbers!

-Puma, Pue, Pume, Pusho (6,7, 8, 9; or 11, 12, 13, 14)
-Epu(n) (10 / 20), Mepu(n) (15 / 30), Shopu(n) (20 / 40)

Fe(n) - 25 / 100
Ka(l) - 125 / 1000

-Puka(l) (625 / 10000)
-Feka(l) (3125 / 100000)

-Jo (15625 / 1000000)

Then you could guess after Jo, Pujo and Fejo for 78125/10000000 and 390625/100000000!

I need more numbers, of course. Though I think all the way up to 390625 is plenty for now.


Also, the way to express numbers in Meikar, using Latin Numbers, is just as you would here on Earth: 10, 121, 344, etc. But on a sentence line in true Meikar, the numbers 0-4 are X, I, Λ, Δ, ◻. X, I and Λ have dots at their dead ends, as usual with Meikar characters.

Numbers in Olea:

0 tu
1 ise
2 da
3 mu
4 na
5 alu
6 ani
7 ela
8 etu
9 nape
10 ta

11-19: taise, tada, tamu, tana, tahalu, tahani, taela, taetu, tanape

20 data 60 anita 101 seteise 1960 mutu napesete anita
21 dataise 70 elata 200 datete 2000 damutu
30 muta 80 etuta 300 mutete 10000 natu
40 nata 90 napeta 562 alutete anitaise 100000 alutu
50 aluta 100 tete 1000 mutu 1000000 anitu

Here are the numbers 0-10 in my conlang, Fenx. First cardinal, then ordinal, then fractional:

0 nule, nuleghish, nulehedish
1 dann, dannish, dannghedish
2 drie, drieghish, drieghedish
3 thrice, thriceghish, thricédish
4 phen, phennish, phenghedish
5 faighr, faighrish, faighredish
6 seghay, seghayghish, seghayghedish
7 seghacht, seghachtish, seghachtedish
8 loch, lochish, lochghedish
9 ngry, ngryghish, ngryghedish
10 dac, daccish, daccedish

Wow, you have separate endings for ordinal and fractional? That's cool. It's not a common feature to see.

Hello! Throwing in my 2¢ here:
Síyähärä (Yaharan for convenience) works off Base Twelve, so I'll leave one through twelve plus some. *note: I use Tibetan 1 and 2 to represent ten and eleven*
One - 1 - Onën
Two - 2 - Ës
Three - 3 - Tän
Four - 4 - Bisíg
Five - 5 - Du
Six - 6 - Tünd
Seven - 7 - Gifíg
Eight - 8 - Fän
Nine - 9 - Ke
Ten - ༡ - Dös
Eleven - ༢ - Vös
Twelve - 10 - Nyö
Thirteen - 11 - Nyönën
Fourteen - 12 - Nyös
Fifteen - 13 - Nyötän
Sixteen - 14 - Nyöbisíg
...
Twenty-one - 19 - Nyöke
Twenty-two - 1༡ - Nyödös
Twenty-three - 1༢ - Nyövös
Twenty-four - 20 - Lösë
Twenty-five - 21 - Lösëönën
...
Thirty-six - 30 - Trösë
Fourty-eight - 40 - Nösë
Sixty - 50 - Glösë
Seventy-two - 60 - Þëtë
Eighty-four - 70 - Ÿsþönë
Ninety-six - 80 - Nocë
One h. and eight - 90 - Kolÿþë
One h. and twenty - 100 - Kolÿþu
One h. and thirty-seven - 111 - Kolÿþunnyönën
One h. and forty-nine - 121 - Kolÿþunlösëës

*Edit: Use for both cardinal and ordinal numbers*

Numbers in my Conlang Hannish (Hanske,) enjoy!
0- nil
1- en
2- dve
3- þrir
4- fær
5- fem
6- seks
7- søve
8- otte
9- nyv
10- tyv
11- entin
12- dvetin
13- trirtin
14- færtin
15- femtin
16- sekstin
17- søvetin
18- ottetin
19- nyvtin
20- dvety
21- dvetyogen
22- dvetydve
23- dvetyþrir
24- dvetyfær
25- dvetyfem
100- hyndre
1000- tusend
10000- tyvtusend
100000- hyndretusend
1000000- mølger
10000000- tyvmølger
100000000-hyndremølger
1000000000-bølger
10000000000- tyvbølger
100000000000- hyndrebølger
1000000000000- trølger
10000000000000- tyvtrølger
100000000000000-hyndretrølger
1000000000000000- færger
10000000000000000- tyvfærger
100000000000000000- hyndrefærger
1000000000000000000- femger
10000000000000000000- tyvfemger
100000000000000000000- hyndrefemger
1000000000000000000000- seksølger
10000000000000000000000- tyvseksølger
100000000000000000000000-hyndreseksølger
1000000000000000000000000-søvenølger
10000000000000000000000000-tyvsøvenølger
100000000000000000000000000- hyndresøvenølger

example number- 123 456 789 (one hundred twenty three million four hundred fifty six thousand seven hundred eighty nine.) En hyndre dvety þrir mølger fær hyndre femty seks tusend søve hyndre otty nyv.